1. Field of the Invention and Related Art
This invention relates to a control method for a both-surface recording apparatus, and more particularly to a method of controlling the order or sequence of pages recorded by a both-surface recording apparatus which effects recording, for example, on the front and back surfaces of a recording medium. This invention further relates to a printer apparatus capable of both surface or multiplex printing, and in particular to a control system for a printer (recording apparatus) in which a plurality of cut-sheet-like paper leaves (recording mediums) are caused to make the circuit of round and through the machine, thereby accomplishing both-surface or multiplex printing.
An example of the prior art will first be described with reference to the accompanying drawings.
FIG. 1 is a longitudinal cross-sectional view schematically showing the construction of an image forming apparatus. In FIG. 1, the reference numeral 1 designates a sheet supply cassette containing a number of sheet materials 2 therein, the reference numeral 3 denotes a sheet supply roller as feeding means for feeding the sheet materials 2 in the sheet supply cassette 1, the reference numeral 4 designates register rollers for effecting the positioning and timing of a sheet material 2 fed by the sheet supply roller 3, the reference numeral 5 denotes image forming means for transferring a toner image onto the sheet material 2 by an electrostatic system, the reference numeral 6 designates fixing rollers for fixing the toner image on the sheet material 2 passed through the image forming means 5, the reference numeral 7 denotes a sheet discharge tray as discharge means for containing the sheet material 2 discharged, the reference numeral 8 designates a first conveyance path, the reference numeral 9 denotes a second conveyance path, the reference numeral 10 designates a third conveyance path, and the reference numeral 11 denotes a branch-off conveyance mechanism installed at the branch-off position of the first conveyance path 8, the second conveyance path 9 and the third conveyance path 10. The first conveyance path 8 extends from the sheet supply roller 3 to the front of the fixing rollers 6 via the image forming means 5. The second conveyance path 9 connects the downstream side end of the first conveyance path 8 and that side of the first conveyance path 8 which is upstream of the image forming means 5 (between the register rollers 4 and the sheet supply roller 3). The third conveyance path 10 connects the downstream side end of the first conveyance path 8 and the tray 7 which is the discharge means.
The branch-off conveyance mechanism 11 has deflecting means (flapper) 12 capable of changing between two positions by leftward rotation or rightward rotation, first forward and reverse conveying means (forwardly and reversely rotatable rollers) 13-15 disposed on the second conveyance path 9 side and the third conveyance path 10 side, the second forward and reverse conveying means (forwardly and reversely rotatable rollers) 16. Thus, the deflecting means 12, when in its rightwardly rotated position as indicated in solid lines, connects the first conveyance path 8 and the third conveyance path 10 and directs the sheet material 2 conveyed along the first conveyance path 8 toward the third conveyance path 10. The deflecting means 12, when in its leftwardly rotated position as indicated by broken lines, connects the first conveyance path 8 and the second conveyance path 9 and directs the sheet material 2 conveyed along the first conveyance path 8 toward the second conveyance path 9. The first forward and reverse conveying means 13-15 are adapted to convey the sheet material 2 directcd from the first conveyance path 8 to the second conveyance path 2 side intactly toward the second conveyance path 9 during the forward rotation thereof, and to change the direction of movement of the sheet material 2 and direct the sheet material 2 toward the third conveyance path 10 during the reverse rotation thereof. The second forward and reverse conveying means (rollers) 16 are adapted to convey the sheet material 2 directed from the first conveyance path 8 to the third conveyance path 10 intactly toward the third conveyance path 10 during the forward rotation thereof (at this time, they serve also as sheet discharge rollers), and to change the direction of movement of the sheet material 2 and direct the sheet material 2 toward the second conveyance path 9 during the reverse rotation thereof.
In FIG. 1, the reference numerals 17 and 18 designate forwardly rotatable conveying rollers installed at the upstream end and the downstream end, respectively, of the first conveyance path 8. The reference numeral 50 designates a back surface record sheet supply opening, and the reference numeral 60 denotes a front surface record sheet supply opening.
Referring to FIG. 2, the rollers 16 are being rightwardly rotated, and when the trailing end of the sheet material has passed through the deflecting means 12, the rollers 16 are leftwardly rotated to reconvey the sheet material as shown in FIG. 3.
In the above-described example of the prior art, however, the time required from after the trailing end of the recording medium after the recording on the first surface thereof has passed through the image forming means 5 until the recording medium is directed to the third conveyance path 10 and is reversed by the second forward and reverse conveying means 16 and is directed to the second conveyance path 9 for recording to be effected on the second surface thereof by the image forming means 5 is much longer than the time required for at least the recording medium 2 to pass through the image forming means 5. Therefore, the interval between the first surface recording and the second surface recording during both-surface recording becomes great, and this has led to the inconvenience that the throughput is much reduced.
Another example of the prior art will hereinafter be described in detail by mode with reference to FIG. 4.